Control apparatus for a gas driven pump

ABSTRACT

A gas driven pump (102) is controlled by an asynchronous controller (101). The controller (101) has two control conduits (105,103) respectively in communication with the bottom and top regions of the chamber of the pump (102). Low pressure air is bubbled through the control conduit (105) in communication with the bottom region of the pump chamber; therefore, the pressure in that conduit, which is applied to the face top of the diaphragm (111), in a direct function of the depth of the liquid in the pump chamber. The other control conduit (103) is in communication with the bottom face of the diaphragm (111). When the difference of the pressures in the control conduits (105,103) exceeds the bias of the spring (114), the diaphragm (111) and the attached spool (128) move downward to activate a mechanically operated pilot valve (144). The pilot valve, in turn, releases supply air under pressure to switch the main valve (145) from the rest state to the operated state to initiate discharge of liquid by the pump. When the level of the liquid in the pump chamber falls to a point where the difference in the pressures in the control conduits reaches a second threshold value, the diaphragm moves upward to the rest state; the pilot valve and the main valve are deactivated; and the pump,enters the fill state.

TECHNICAL FIELD

This invention relates to gas driven pump systems which adapt thepumping rate to the rate of liquid flow into the pump environment.

BACKGROUND ART

Gas driven pumps are used in a variety of applications. In someapplications, the pumping capacity is less than the rate at which liquidflows into the pump environment; and in other applications the pumpingcapacity is greater than the rate of liquid inflow. In the former case,pumping rates are established in accordance with considerations otherthan the level of liquid in the pump environment. For example, in someapplications an ejector pump is cycled through fill and dischargeperiods purely on the basis of time.

Where the pumping capacity exceeds the rate of liquid inflow, a numberof mechanical and/or electrical devices e.g., floats, probes andswitches have been employed to detect liquid levels to initiate andterminate pumping. Some mechanical and electrical devices are aliability in a liquid pumping environment; and they are particularlytroublesome in an environment of dirty and/or chemically active orcombustible liquids.

STATEMENT OF THE INVENTION

In accordance with the present invention a gas driven pump whichcomprises: a pump chamber; liquid inflow and liquid outflow portsconnected to the bottom of the pump chamber: and a vent/pressurizingport further comprises: pump control means for sensing differences inpressures at the top and the bottom of the pump chamber; and means forinitiating pumping when the difference reaches a first threshold valueand for stopping pumping when the difference subsequently reaches asecond threshold value. Advantageously, the control apparatus inaccordance with this invention accomplishes pump control without theintroduction of any mechanical and/or electrical devices into the pumpedliquid. The use of differential pressure as the control input results inlittle stress on the control elements; and allows a very sensitivedetermination of the depth of liquid in the pump chamber.

Additionally, since the control is entirely pneumatic, the pump and itscontrols are intrinsically safe.

THE DRAWING

The invention is illustrated more or less diagrammatically in thedrawing wherein:

FIG. 1 illustrates one embodiment of a pump system in accordance with myinvention in the fill state;

FIG. 2 illustrates the pump system of FIG. 1 in the discharge state;

FIG. 3 illustrates a second embodiment of a pump system in accordancewith my invention.

DETAILED DESCRIPTION

The pump system of FIG. 1 comprises the pump 102, the pump controller101 and the interconnecting conduits 103, 104 and 105. The variousvalves of the system of FIG. 1 and the lines which indicate direction offlow are illustrated for the "fill" state of the pump. The pumpcontroller 101 may be mounted directly on top of the pump or may belocated at a point remote from the pump. When the controller 102 ismounted on top of the pump 102, the conduit 104 is merely a hole in thetop of the pump 101 and a connecting hole in the bottom of thecontroller 102.

The pump 102 has an inflow port 107 with a valve 108 which permitsliquid to flow into the pump chamber and prevents outward flow of liquidthrough the port 107. The outflow port 109 includes the valve 110 whichprevents the flow of liquid into the chamber through that port. Thevalves 108 and 110 may be check valves as illustrated in the drawing orthey may be pneumatic or otherwise operated valves which are notillustrated in the drawing.

In FIG. 1, liquid flows in and out of the pump chamber through thecommon opening 106. While this is a convenient structure, the liquidinflow and outflow can be via separate openings in the pump walls. Inany event, the bottom end of the control conduit 105 is advantageouslyplaced opposite the bottom wall of the pump chamber and not opposite anopening therein.

The control conduits 104 and 105 respectively couple the upper region ofthe pump chamber to the lower face of the diaphragm 111 and its backingplate 112; and the lower region of the pump chamber to the upper face ofthe diaphragm 111. Accordingly, the position of the diaphragm isinfluenced by the difference in the pressures which are present in theupper and lower regions of the pump chamber and by the force of the biasspring 114. Additionally, the spring loaded detent balls 118, 119, whichengage the detent recesses in the spool 128, tend to keep the spool 128and the attached diaphragm in the current state.

In the "fill" state, the liquid which flows in through the port 107displaces air in the chamber and that air is vented through the opening137 in the main air valve 145. As seen in FIG. 1, fresh air or gas fromthe air supply conduit 133 is supplied to the controller housing atessentially zero pressure through the choke 131. Accordingly, thepressure on the lower face of the diaphragm 111 and its backing plate112 is the pressure in the upper region of the pump chamber. If theliquid in the pump chamber is above the lower end of the control conduit105, the pressure in the upper region of the pump chamber also acts onthe top surface of that liquid.

Additionally, in the "fill" state, air through the choke 135 is fed toand bubbled through the liquid via the control conduit 105. Accordingly,the pressure of the air in the control conduit 105, and thus acting onthe top face of the diaphragm 111, is determined by the height of theliquid in the chamber and the pressure in the top of the chamber. Sincethe pressure in the top of the chamber acts on both faces of thediaphragm 111, the net force on the diaphragm is that which is due tothe height of the water.

When the difference in pressure on the two faces of the diaphragmexceeds the restraining force of the detents 118 and 119 and the forceof the bias spring 114, the diaphragm and the attached spool 128 will"snap" down to the operated state of the diaphragm. As illustrated inFIG. 1, the diaphragm is at the "rest" state. The function of the pumpcontrol when the diaphragm 111 is in the "operated " state is bestunderstood from a description of FIG. 2 which illustrates the dischargeof liquid from the pump.

In FIG. 2, the diaphragm 111, the backing plate 112 and the rod 128 areillustrated in the "operated state" of the diaphragm. In that state, thecamming surface 127 of the rod 128 forces the ball 125 into the body ofthe pilot valve 144 to provide an air path between the pilot valveoutput conduit 129 and the conduit 130, which is connected to a sourceof relatively high pressure air or gas which is supplied via conduit133. When this air source is applied to the control port of the mainvalve 145, the main valve will change from the "fill" state to the"discharge" state.

In the discharge state, the main valve 145 provides an air path betweenthe source conduit 133 and the conduit 138. As the pressure in the upperregion of the pump chamber 102 consequently rises, the valve 108 willclose and the valve 110 will open. Accordingly the liquid in the pumpchamber 102 will be ejected through the output port 109 which conveysthe liquid to a planned destination. As the liquid is ejected from thepump chamber 102, the difference in pressure between the upper and lowerregions of the pump chamber falls. When the difference reaches a secondthreshold value, the force of the compressed spring 114 will overcomethe restraining force of the detents 118 and 119 in the upper annularrecess in the rod 128, and the diaphragm 111 will snap back to the reststate to again initiate the fill state of the pump.

While the pump is in the discharge state, high pressure fresh air fromconduit 138 is transmitted to the upper and lower portions of thecontrol chamber by the conduits 151 and 153. The introduction of freshair into the control chamber prevents the flow of possibly harmful gasesinto the control chamber from the pump chamber. The gases which mayoccur in the pump chamber could be harmful to the control apparatus. Inthe fill state, the spring loaded check valves 154 and 150 isolate thecontrol chamber from the conduit 138.

In the embodiment of FIG. 3, the controller 301 is mounted directly ontop of the pump chamber 302; the diaphragm 111 is replaced by two spacedapart diaphragms 360 and 370; and the pressure in the lower portion ofthe pump chamber is conveyed to the controller by a liquid filledassembly which includes the compressible member 350 and the conduit 351.The control chamber between the diaphragm 360 and the diaphragm 370 maybe filled with gas under pressure to reduce strain on the controlassembly.

As in FIG. 1 and FIG. 2, the controller 301 of FIG. 3 responds to thedifference in pressures in the upper and lower regions of the pumpchamber to asynchronously cycle the pump through fill and dischargecycles. Since the pressure in the upper portion of the pump chamber isapplied to both the bottom face of the lower diaphragm 370 and to thecompressible tube 350, the difference in the pressures which are appliedto the diaphragm 360 and the diaphragm 370 is due soleley to the heightof the liquid in the chamber 302.

In FIG. 3, the controller assembly is shown in the pump fill mode. Inthat mode, liquid is free to flow into the pump chamber through theinput port 307; and the output port 309 is blocked by operation of thevalve 310. As the liquid flows into the chamber, the air or gas in thepump chamber is vented through a path which includes: conduit 303, apath through the main air valve 344 and the vent conduit 337. As theliquid rises in the pump chamber, the member 350 is compressed and theliquid therein tends to force the diaphragm assembly downward. When thesum of the force applied to the upper face of the diaphragm 360 and theforce of the compressed coil spring 328 exceeds the sum of the forceapplied to the lower face of the diaphragm 370, the restraining force ofthe pilot valve ball 325 against the camming surface 362 and therestraining force of the detent assembly, the diaphragm assembly willsnap downward to the discharge state. In that state, the ball 325 ismoved into the body of the pilot valve 345 to connect air from thesource conduit 333 to the control input conduit 329 of the main airvalve 344. This activates the main air valve which blocks the path tothe vent conduit 337 and connects the air source conduit 333 to the uppeportion of the pump chamber via the conduit 303. As the air enters thepump chamber, the valve 308 is closed, the valve 310 is opened andliquid is ejected through the output port 309.

As the liquid is ejected from the pump chamber 302, the pressure whichis applied to the upper face of diaphragm 360 falls. When the pressureat the upper face of the diaphragm 360 reaches a second threshold value,the spring 328 is compressed; the control assembly is restored to therest state; the pilot valve 345 and the main valve 344 are deactivated;and the fill mode is reactivated.

As compared to the physical placement of the bias spring 114 of FIGS. 1and 2, the bias spring 314 of FIG. 3 is placed to have a bias effectopposite to that of spring 114. In FIGS. 1 and 2, the bias spring 114urges the diaphragm 111 toward the "fill" or rest state. In FIG. 3, thebias spring is placed to bias the diaphragm assembly toward thedischarge state. In FIG. 3, the liquid in the compressible chamber 3251and the conduit 351 tends to draw the diaphragm 360 upward toward the"discharge" state. The function of the bias spring 314 is to overcomepart of that upward force and to set the "operating" point of thediaphragm to initiate and terminate pumping when the depth of water inthe pump reaches corresponding predetermined values.

The embodiments shown and described herein are only illustrative of theteaching of my invention and many changes in detail may be made withoutdeparting from the spirit and scope of my invention.

What is claimed is:
 1. A gas driven pump system comprising:a rigidelongated tubular body defining a pump chamber and comprising: top,bottom and side walls; liquid inflow conduit means in communication withsaid chamber through said bottom wall; first liquid valve means forpreventing flow of liquids out of said chamber through said inflowconduit means; liquid outflow conduit means in communication with saidchamber through said bottom wall; second liquid valve means forpreventing flow of liquids into said chamber through said outflowconduit means; main air conduit means in communication with said chamberthrough an opening in or near said top end of said body for conveyinggases from and to said chamber for selectively venting and pressurizingsaid chamber; control reference pressure conduit means in communicationwith said chamber; one end of said reference pressure conduit meansextending outside said body and the other end thereof positioned in ornear said top end of said body; control high pressure conduit means incommunication with said chamber; one end of said high pressure conduitmeans extending outside said body, and the other end thereof beingpositioned in said chamber near said bottom end of said body; a sourceair conduit means for connection to a source of air or gas underpressure; bubble source conduit means including a restriction thereincoupling said source air conduit means to said high pressure conduitmeans for providing gas at essentially zero pressure to said highpressure conduit means; switching means comprising: an air supply inputport for connection to said source air conduit means; a vent port; amain air port connected to said main air conduit means; and means forselectively connecting said main air port to said vent port in one stateof said switching means and for connecting said air supply port to saidmain air port in a second state of said switching means; sensing meanscomprising: means coupled to said control reference conduit means forsensing the pressure within said chamber at or near the top end thereof;means coupled to said control high pressure conduit means for sensingthe pressure within said chamber at or near the bottom end thereof; andmeans for controlling said switching means to switch from said one stateto said second state and to restore said switching means to said firststate as a function of the difference between the pressures sensed insaid top and bottom ends of said chamber; and first and second purge airconduit means for respectively coupling said main air conduit means tosaid control reference conduit means and to said control high pressureconduit means; said purge air conduit means each comprising gas flowcheck valve means permitting air to flow from said main air conduit andpreventing the flow of air in the opposite direction.
 2. An ejector pumpsystem in accordance with claim 1 wherein: said liquid inflow conduitmeans and said liquid outflow conduit means are in communication withsaid chamber through a common opening in said body.
 3. A gas driven pumpsystem in accordance with claim 1 wherein: said sensing means controlssaid switching means to switch from said one state to said second statewhen the difference in pressures in said reference and said highpressure conduits rises to a threshold value, and controls saidswitching means to switch back to said one state when the difference inpressures in said conduits subsequently falls below a second thresholdvalue which is less than said first threshold value.
 4. A control for agas driven pump system in accordance with claim 1 wherein: said sensingmeans comprises a flexible diaphragm movable between a rest position andan operated position; one side of said diaphragm being in communicationwith said reference conduit and the other side of said diaphragm beingin communication with said high pressure conduit.
 5. A gas driven pumpsystem in accordance with claim 1 wherein: said switching meanscomprises a mechanically operated pilot valve and an air operated mainvalve controlled by said pilot valve.
 6. A gas driven pump system inaccordance with claim 1 wherein:said sensing means comprises a flexiblediaphragm movable between a rest position and an operated position; oneside of said diaphragm being in communication with said referenceconduit means and the other side of said diaphragm being incommunication with said high pressure conduit means, said switchingmeans comprises a mechanically operated pilot valve assembly coupled toand operated by motion of said diaphragm and an air operated main valvecontrolled by said pilot valve.
 7. A gas driven pump system inaccordance with claim 6 wherein: said pilot valve assembly comprises abias spring for applying a force which urges said diaphragm to said reststate in which said pilot valve is closed and said main valve is in theone state.
 8. A gas driven pump system in accordance with claim 7wherein:said pilot valve assembly comprises a roller operated pilotvalve comprising a T shaped body and a spring loaded roller ballprotruding from one leg of said body; a spool block having a spoolpassage therethrough; a spool slidable in said spool passage and havingone end affixed to said diaphragm; an operator passage in said spoolblock in communication with said spool passage for receiving said oneleg of said pilot valve body; and said spool comprises a cam surfacedisposed adjacent said operator passage when said diaphragm is at therest position and positioned opposite said operator passage and inoperative engagement with said roller ball when said diaphragm is at theoperated position.
 9. An ejector pump system in accordance with claim 8wherein: said pilot valve assembly further comprises: a spring loadeddetent assembly mounted in said spool block and protruding into saidspool passage; andsaid spool comprises at least one detent depressionfor engaging said detent assembly.